ByCatherine Lucey and Ken Thomas, Associated PressAugust 18, 2014

Then-Secretary of State Hillary Rodham Clinton, and former President Bill Clinton, listen to speakers in Washington, in 2011. The Clintons will headline the annual steak fry on Sept. 14, 2014, for retiring Sen. Tom Harkin of Iowa, making a big return to the leadoff caucus state as Mrs. Clinton considers another presidential campaign.

DES MOINES, Iowa — Bill and Hillary Rodham Clinton will headline the annual steak fry for retiring Sen. Tom Harkin of Iowa, making a big return to the leadoff caucus state as the former secretary of state considers another presidential campaign.

Sam Roecker, a spokesman for the Harkin Steak Fry, said Monday that both Clintons will speak at the fundraiser in Indianola, just south of Des Moines, on Sept. 14. It will be the former first lady's first appearance in Iowa since 2008, when she finished a disappointing third in the caucuses. She is the leading Democratic presidential contender, and the event is among her first campaign appearances before the 2014 midterm elections.

This will be Hillary Rodham Clinton's second Steak Fry appearance and Bill Clinton's fourth time at the event.

Clinton has said she intends to campaign for Democratic candidates this year. Iowa is the home of a key Senate race, with Democrat Bruce Braley opposing Republican Joni Ernst. Iowa's presidential caucuses will begin the 2016 nomination process.

Democrats said she is expected to appear at campaign events for the four major Democratic fundraising committees but details were still being determined.

For Clinton, the campaign appearances could serve as an unofficial start of a presidential campaign, should she decide to run, and will allow her to appeal to Democrats looking for a successor to President Barack Obama. Clinton has urged Democrats to mobilize for the midterm elections and try to maintain a Senate majority, which would be crucial for Obama's final two years in office.

"If I decide to run, I will have a very specific agenda about what I think we should be doing. But right now, we have a big election, midterms 2014, that could determine the control of the Senate," Clinton said in an interview in July. "And I'm not going to, you know, jump the line and start talking about 2016 right now."

The steak fry, which will be Harkin's final as a sitting senator, is expected to be a tribute to the veteran lawmaker, who has longstanding ties to the Clintons. Speaking at the event is coveted among national Democratic figures and it raises money for the state party, which will help Democratic campaigns up-and-down the ballot. Last year, Vice President Joe Biden headlined the event.

"Secretary Clinton is an extraordinary force for our values and will relentlessly fight to jumpstart the middle class," said Rep. Steve Israel, chairman of the Democratic Congressional Campaign Committee. "We're thrilled and grateful that she is lending her support to our shared goal of electing a Democratic House of Representatives that will put a stop to the endless cycle of dysfunction and shutdowns from this Republican Congress."

In October, Clinton is expected to appear at a fundraiser in San Francisco for female candidates with House Democratic leader Nancy Pelosi, D-Calif.

Iowa has had few visits from Democrats considering a 2016 presidential run. Biden came last year and Maryland Gov. Martin O'Malley has visited this year, campaigning for Democrats. Though Clinton has not been in the state, the Ready for Hillary organization has been working her on her behalf.